T.L.
First thing, maybe you should go visit a friend with a newborn and be reminded of what it's like to have a new one at home!! Maybe it will make you change your mind real quick! :) haha
But....
I feel your pain. My DD is almost five and she's still an only child! That is about to change in the very near future as I was FINALLY able to convince my hubby, who was like yours, didn't understand the need for a sibling (and he HAS a sister!). Here is what I did, I played the "when we get older SHE, alone, is going to bare the burden of taking care of us, and God forbid if we die at the same time, she is going to be ALL ALONE in the world". If you have seen an in-law or relative having to take care of an aging parent alone, it's heart-breaking. My MIL is an only child and now she has to take care of her mom who has Alzheimers. She has even said she SO wished she had a sibling while growing up, and now when it's her all alone caring for her mom. I also played the "there is no closer <blood wise> relative than a sibling" which is true. God forbid if your child ever came down with a blood disorder, having a blood sibling could save that child's life, as they have the closest matching DNA.
Having a sibling gives the child a person who understands COMPLETELY what they are going through when they are having a rough time, ie, disagreements with the parental units! Use your childhood experiences to show the bond you had with your siblings and how no friend could EVER relate completely.
One major thing I did was work out the logistics, which was a big concern for him. How are we going to afford it, what center is the child going to go to (we both work full-time), etc etc.... If you wait to be able to afford to have kids, you will NEVER have them. He understood that and is finally on board to start trying. He knows how bad I want another child and with some comprimise, and strategic arguing, he's NOW wanting one too!
I wouldn't sneak the IUD out, you will always feel some kind of guilt for that, and I don't think you want to feel that way forever....especially if he EVER suspects anything. I think if you really sit him down, with some great "pros" for adding to your family and really get it across to him how badly you want this, maybe he will concede. If he doesn't, maybe you should take a closer look at your marriage. (Maybe if he wasn't an only child, he wouldn't be such a spoiled brat!!haha) I know women who feel resentment for their hubbys because he didn't want more children, and who wants to live the rest of their lives resenting someone whom they love deeply?? If it doesn't work, my MIL has kittens she's trying to find homes for, maybe that will curb the baby bug! That, or a puppy! :) Good luck!!